EMG power spectra of elbow extensors during ramp and step isometric contractions

  • Martin Bilodeau
  • A. Bertrand Arsenault
  • Denis Gravel
  • Daniel Bourbonnais
Article

Summary

The goal of the present study was to compare electromyogram (EMG) power spectra obtained from step (constant force level) and ramp (progressive increase in the force level) isometric contractions. Data windows of different durations were also analysed for the step contractions, in order to evaluate the stability of EMG power spectrum statistics. Fourteen normal subjects performed (1) five ramp elbow extensions ranging from 0 to 100% of the maximum voluntary contraction (MVC) and (2) three stepwise elbow extensions maintained at five different levels of MVC. Spectral analysis of surface EMG signals obtained from triceps brachii and anconeus was performed. The mean power frequency (MPF) and the median frequency (MF) of each power spectrum were obtained from 256-ms windows taken at 10, 20, 40, 60 and 80% MVC for each type of contraction and in addition on 512-, 1024-and 2048-ms windows for the step contractions. No significant differences (P>0.05) were found in the values of both spectral statistics between the different window lengths. Even though no significant differences (P>0.05) were found between the ramp and the step contractions, significant interactions (P<0.05) between these two types of contraction and the force level were found for both the MPF and the MF data. These interactions point out the existence of different behaviours for both the MPF and the MF across force levels between the two types of contraction.

Key words

Electromyograpresentphy Power spectral analysis Ramp/step isometric contractions 

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Martin Bilodeau
    • 1
    • 2
  • A. Bertrand Arsenault
    • 1
    • 2
  • Denis Gravel
    • 1
    • 2
  • Daniel Bourbonnais
    • 1
    • 2
  1. 1.School of Rehabilitation, Faculty of MedicineUniversity of MontrealCanada
  2. 2.Research CentreMontreal Rehabilitation InstituteMontrealCanada

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